Electron discharge device



June 27, 1950 D. v. EDWARDS ETAL 2,512,519

4 ELECTRON DISCHARGE DEVICE Filed Aug. 21, '1947' 3 Sheets-Sheet l FlakZ.

Summers DY Edwards and W. G-Br'own.

MMM

Their Cmorneg D. v. EDWARDS ETAL 2,512,619

ELECTRON DISCHARGE DEVICE June 27, 1950 3 Sheets-Sheet 2 Filed Aug. 21,1947 lvllllllllllllll 6 3nvcntor DAV Edwards and W.G.Br own u TheirGttorneg June 27, 1950 p v EDWARDS ETAL 2,512,619

ELECTRON DISCHARGE DEVICE Filed Aug. 21, 1947 3 Sheets-Sheet 3 SnncutorsDVEdwcLr'ds and WGBr'own Their (momeg Patented June 27, 1950 ELECTRONDISCHARGE DEVICE Donald V. Edwards, Montclair, and Warren G. Brown, WestEnglewood, N. J., assignorsto Electrons, Incorporated, Newark, N. J., acorporation of Delaware Application August 21, 1947, Serial No. 789,876

I 19 Claims. (Cl. -250-2'l.5)

. 1 This invention relates to hard vacuum electro discharge tubes, andmore particularly to such tubes of the triode type for use incross-magnetizing magnetic fields and capable of providing relativelylarge anode current for power oscillators, inverters and the like.

In one type of hard vacuum triode, such as disclosed for example in theprior application of J. H. Burnett, Ser. No; 647,007, filed February 12,1946, and termed for convenience a magnatriode, the thermionic emissivecathode, control element or grid, and the anode or plate characteristicof the typical triode are specially organized and disposed in a strongcross-magnetizing magnetic field, so that relatively high positivepotentials may be applied to the control element or grid and obtainlarge anode currents without appreciable electron current to saidcontrol element.

The primary object of this invention is to provide a structuralorganization and arrangement of parts for a magnatriode of this type,which will establish and maintain under the operating conditions oftemperature and the like, the desired space relationship of the tubeelements, and also afiord appropriate areas of the cathode emissivesurfaces, control elements and anodes for relatively large anodecurrents within over-all dimensions suitable for providing efilciently astrong magnetic field through the tube.

Various other objects, attributes, and advantages of this invention willbe in part apparent, and in part pointed out as the descriptionprogresses.

By way of general explanation, and without attempting to define thenature and scope of this invention, it is proposed to support aplurality of narrow elongated flat grid bars in parallel relation with aplurality of filamentary cathodes, one between each pair of grid bars,between the opposing surfaces of an enclosing anode, all insuch a mannerto permit expansion of the grid bars and cathodes at the operatingtemperatures without material distortion of their space relation: tomaintain an endwise tension on the cathodes when heated to cooperatewith the cross section of the cathodes to resist their displacement by afiow of heating current in them while in the magnetic field, and toemploy simple expedients for mounting and supporting the parts in thedesired space relationship,- using insulated elements required towithstand the cathode heating voltage only. This is merely .a' generalexplanatory summary of some of the significant features of theinvention; and the significance of these features, and various otherstructural characteristics of the invention will appear hereinafter.

The accompanying drawings illustrate one specific and typical embodimentof the invention,

certain parts being illustrated in a somewhat schematic and diagrammaticfashion, more with- Fig. 2 is a fragmentary and diagrammatic view forexplanatory purposes of a transverse section of what may be termed anelemental unit of the magnatriode type of tube.

Fig. 3 is one view of the general organization of the tube of thisinvention, in the form of a longitudinal section through the tube, withpart of the anode broken away.

Fig. 4 is another longitudinal section through the tube in another planealong the line 4-4 indicated in Fig. 3.

Figs. 5 and 6 are two transverse sections through the tube of Figs. 3and 4 along the lines 5-5 and 6--6 respectively in Fig. 3.

Figs. '7 and 8 are fragmentary enlarged views showing certain details ofconstruction for the anchorage of the ends of the cathodes and the typeof cathode insulators preferably employed.

Before discussing in detail the structural features of the embodiment ofthe invention shown, it wduld appear to be expedient to consider thegeneral organization and functions of what may be termed an elementalunit of the magnatriode type of tube, as illustrated in Fig. 2. Suchelemental magnatriode unit, which in efiect is the basisfor the tubestructure of this invention, comprises a suitable thermionic emissivecathode C of an elongated or filamentary form, which.

is disposed between two parallel anodes A, A and two elongated grid barsG, G as indicated in Fig. 2, it being assumed that the cathode C, anodesA, A and grid bars G, G shown in cross section will have the appropriatelength. This organization of tube elements, within'a suitable evacuatedenvelope (not shown), is disposed in a strong uni-directionalmagnetic'field, such as provided between the pole pieces designated Nand S of a permanent magnet or equivalent Briefly considering thepurpose and advantages of this arrangement of tube elements in amagnetic field, it is contemplated that the cathode C will be capable ofemitting a surplus of electrons for the operating voltages, so that theanode current is space charge limited. The potentials on the grid barsG, G serve to supplement or neutralize this space charge and control theelectron current from the cathode to the anodes A, A In this connection,it can be seen that negative potentials on the grid bars G, (3- tend toreduce the anode current, and it sufliciently large will cut otf anodecurrent, while positive potentials will act to neutralize the effect oi!the space charge to increase the anode current, and also tend toincrease the potential at the cathode surface to draw more electronsfrom the cathode. The magnetic field, indicated bythe arrow H, which isa cross-magnetizing field with respect to the cathode, may be said tohave in general the effect of converging or focusing the electronsleaving the cathodes into streams or beams, such as indicated by dottedlines 5 in Fig. 2, this focusing action being in accordance with thewell known principles relating to the movement of electrons in magneticfields.

Assuming a magnetic field otthe appropriate strength with respect to thetube elements and voltages involved, a relatively high positivepotential may be applied to the grid bars G, G and result in large anodecurrents, without having electron current to the grid and grid lossescharacteristlc of the usual type of triode, because the magnetic fieldacts to confine the stream of electronspassing from the cathode to theanodes to paths which miss or escape the grid barsin spite of thepositive potential thereon.

The use of such an arrangement 01' tube elements in a cross-magnetizingfield, in the manner characteristic of the magnatriode type oi. tube andschematically illustrated in Fig. 2, affords operating characteristicsfor tubes 01' the hard vacuum triode type, which may be advantageouslyemployed in various applications of triodes, such as amplifiers, poweroscillators, inverters and the like; but since the particular use orapplication 01 this type of tube is not material to this invention, andforms the subject matter of other applications, it is not necessary todiscuss further the operating characteristics and advantages of themagnatriode. Also, the magnatriode type of tube is disclosed and claimedin other applications such as that of J H. Burnett above mentioned; andno claim is made herein to the basic features of such a tube and variousstructural characteristics disclosed and claimed in these otherapplications.

For a tube having the features of the elemental form of magnatriodeillustrated in Fig. 2, which is capable of providing large anodecurrents and utilizing high voltages for power purposes and the like, itis desirable-to increase the eflective areas of the cathode, anodes andgrid bars of the elemental unit, while maintaining the desiredrelatively close space relationship of these tube elements under theoperating conditions oi temperature and the like. There are variousrequirements to be satisfied for such a, power tube structure. Amongother things, it is desirable that the tube should have over-alldimensions 4 suitable for use in small airgaps of magnetic circuits, sothat a strong magnetic field may be obtained from themagneto-motive-force employed, such as from a permanent magnet or thelike. During operation of the tube, the cathodes and grid bars tend toassume relatively high temperatures in such a compact assembly; andappropriate expedients have to be adopted for mounting and supportingthese elements to permit their elongation and expansion withoutmaterially affecting the relatively close relationship desirable. Also,in this type of tube the cathode is subjected'to a sidewise bending ordisplacing force due to the reaction of the magnetic field in which thetube is used and the magnetic field created by the current flowing inthe cathode; and it is desirable to employ, in addition to a crosssection suitable to resist such bending force, a supporting arrangementwhich will serve to maintain an endwise tension on the cathode after itis heated. In addition to these requirements typical of a tube of thistype, it is desirable to provide forms of support and electricalisolation of the various parts in the desired close relationship, in amanner which will permit the use of high voltages. More particularly,where insulators are employed to obtain the desired space relationshipof parts, it is desirable that these insulators be subjected to thelower voltages involved, such as the cathode heating voltage, and shouldalso be located so as to keep relatively cool during the operation ofthe tube.

After this brief summary of some of the problems sought to be solved bythis invention, consideration may be given to the structural features ofthe specific embodiment of the invention illustrated. Referring to Fig.1, it is contemplated that the tube of this invention, indicatedgenerally at T, will be disposed in the airgap of a magnetic circuithaving a suitable source of magneto-motive-force, such as a permanentmagnet as indicated in Fig. 1. In the particular arrangement shown inoutline in Fig. 1, which of course is merely typical, the permanentmagnet comprises two curved arms or legs 6, preferably circular in crosssection, of a suitable permanent magnet material, such as the alloycommonly called alnico. The lower ends of these curved arms 6, which areof course magnetized in accordance with recognized practice, areattached to a soft iron base or back yoke 1 in a suitable manner, suchas by' screws or bolts (not shown) threaded into inserts in thepermanent magnet material. rectangular shape are fastened in a similarmanner to the upper ends of the permanent magnet arms 6, with an airgapas small as the dimensions of tube T will permit. The tube T is disposedin the airgap between these pole pieces 8 of the permanent magnet, suchthat the magnetic lines 01' force act in relation to the grid bars andanodes of the tube as indicated in Fig.- 2. As illustrated, it isassumed that this tube T will be supported in an upright position by asuitable base and socket, such as generally indicated in the outline at9, mounted on the back yoke I of the magnet. This of course is merelyone of the various arrangements that may be employed. For someapplications it may be expedient to immerge the tube T and associatedparts in oil for heat dissipation, or provide forced draft air coolingin any one of the well known manners not material to the presentinvention.

It will be evident that, to obtain a strong magnetic field through thetube T for a given Soit iron pole pieces 8 of a general size ofpermanent magnet, the airgap should be short; and for this reason thetube elements are organized and arranged and enclosed in an envelope ofrelatively large width and length, but relatively thin and narrow in itsthickness, so as to have dimensions suitable for disposition in a shortairgap between the pole pieces 8 of substantial area.

Referring to Figs. 3 and 4, the tube of this invention has a suitableenvelope E assumed to be of glass-in the particular structureillustrated. This envelope has a length and width somewhat larger thanthe areas of the pole pieces of the magnetic circuit for the tube, asshown in Fig. 3, but is relatively thin or narrow, as shown in Fig. 4,to conform with the length of the airgap between these pole pieces. Theside walls of the envelope E are straight longitudinally of the tube,but are curved transversely to give a generally elliptical crosssection, as shown in Figs. 5 and 6, so that the walls of the envelopewill have the necessary strength to resist pressure when exhausted. I

Generally speaking, the tube structure of this invention comprises twoof the elemental magnatriode units shown in Fig. 2 arranged side byside. There are three grid bars GI, G2 and G3 arranged in parallelrelation at substantially equal spaced intervals; and this assembly ofgrid bars is supported from the envelope E by a single supporting rod orpost I2 sealed in a flat press I3 at the bottom of the envelope E inaccordance with the usual practice, using the appropriate metal wherethis lead-in and supporting element passes through the glass to afiord agas-tight seal. These grid bars are narrow flat strips" formed fromsheet stock of suitable thickness with longitudinal flanges to give achannel cross section for lateral stifiness (see Fig. 6). These gridbars may also be provided with longitudinal corrugations (not shown) ifdesired. The material for these grid bars should be non-magnetic; andfor many applications, it is desirable to employ a surface oxidized orotherwise treated toreduce the tendency to become emissive at theoperating temperature. Tantalum, molybdenum, nichrome or stainless steelare typical materials suitable for the grid bars, the particularmaterial used being of course dependent upon rating and othercharacteristics of the tube.

The middle grid bar G2 is formed of two strips with their edge flangesoverlapped and welded at their ends in a substantially equally spaced.

parallel relation from a center supporting'post I2, and that theflexible or-yieldable connections I4, I5 for the ends of these grid barspermit them to expand lengthwise individually under changes intemperature, without materially changing their relationship to eachother or other parts of the tube.

There are two filamentary or elongated cathodes CI and C2 in the tubestructure of this invention which respectively extend longitudinallybetween an adjacent pair of grid bars GI, G2 and G2 and G3, parallelwith'the surfaces of these grid bars and spaced at substantially equaldistances therefrom. As shown, these cathodes CI and C2 are in the formof flattened tubes disposed edgewise to' the grid bars (see Fig. 6) soas to have a cross section for resisting bending sidewise toward thesegrid bars, due to what may betermed the motor action characteristic ofthe magnatriode type of tube. For example, referring to the elementaltube unit of Fig. 2, it can be seen that the cathode C, when heated bycurrent in the usual way, is ineffect a wire carrying current disposedin a magnetic field acting in the direction indicated by the arrow H;and in the same way that any wire carrying current in a magnetic fieldhas a force exerted thereon, a force is exerted sideways upon thiscathode C, inone direction or the other dependent upon the direction offlow of current tubular form disposed edgewise to the grid bar together;as shown in Fig. 6, and these strips are preferablyarranged to fitclosely around the grid supported post I2 and are welded to this post atsome intermediate point in their length. This affords a substantialsupport for the middle grid bar G2, and yet permits it to expandlengthwise when heated, Theother grid bars GI and G3 are connected attheir upper and-lower ends by flexible cross connectors I4, I5 to theends of the center grid bar G2, such connections leaving openings asshown in Figs. 5 and 6 for the cathodes CI, C2. As shown, each of thesecross connectors I4, I5 comprises two additional angle pieces I4 I5having vertical legs welded to the two strips respectively of the middlegrid bar .G2, and their horizontal legs welded to the conas shown inFig. 6 has its metal disposed in a cross section suitable for resistingthis bending force due to motor action. It is desirable that theycathode CI. and C2 should effectively resist this motor action,otherwise the uniform space relation of thecathode to the grid bars isdisturbed, and the operating characteristics of the tube may beadversely affected. Also, when the cathode is heated by an alternatingcurrent, as it is usually most expedient, this motor action tends tovibrate the cathode, and not only affect the operating characteristicsof the tube, but also tend to weaken the cathode at its emissivetemperature on account of metal fatigue.

In the particular arrangement illustrated, it is assumed that cathodesCI and C2 are tubes of nickel which are flattened, and then coated witha suitable emissive coating, preferably of the barium oxide type, suchas disclosed for example in the prior patent to D, V, Edwards et al.,No. 1,- 985,855, dated December 25, 1934. However, a single strip oftungsten, or thoriated tungsten, may be employed for the cathodes CI andC2.

In addition to the use of a cathode of a cross section suitableforresisting the motor action above discussed, it is also desirable, onaccount of the limitations in the cross sectional area of the metal thatcan be advantageously employed, to provide a mounting support for thesecathodes which will maintain tension lengthwise of these cathodes, afterthey are heated to the emissive temperature. Among other things, thisendwise pull upon the cathodes prevents the motor action from causingsidewise displacement by warping or twisting the cathodes.

The structure illustrated for supporting the cathodes CI and C2comprises two supporting rods 20 sealed in the stem I3 of the envelopeE, and extending outside of this envelope through the usual gas-tightseals to afford external connections for the cathodes and their heatingcircuit.

enlarged or deformed, as indicated'at 23 in Fig.'

8, bywelding or the like, at points under the lower ends of theseinsulators, so that their downward movement is limited. Metallic strips25, constituting what may be termed a cathode header, are formed andwelded together to extend between the insulators 22, and have rings orcollars 25 as shown in Fig. 5, which surround these insulating tubes 22with a close but slidable fit thereon. The upper ends of theseinsulators 22 are formed with shoulders which support a cross member 26;and this cross member 26 is connected to the cathode header by aresilient element 2! (see Fig, 3), which serves to exert an upward pullon the cathode header 25 and apply to the cathodes Cl and C2 the desiredtension when heated.

This resilient element 21 may be a, spirally wound wire 'of tungsten,molybdenum or like material, which after being subjected to a baking andde-gassing procedure, is further deformed to give the desired tension,and then'attached to the cross member 28 and the cathode header 2'! bywelding or mechanical interconnection of parts. For certain types oftubes, it may be expedient to employ springs of steatite or quartz, orotherwise adopt materials and practices of the art to provide aresilient element capable of giving the desired tension'after the tubeassembly is subjected to the appropriate procedure for activation of thecathodes and de-gassing the parts.

The two cathodes Cl and C2 are welded at their upper ends to the cathodeheader 25. For this purpose, the ends of these tubes may be flattened,and an additional piece employed to form a sandwich weld and facilitatewelding operation, as indicated in Fig. 7. The lower ends of the twocathodes Cl and C2 are welded respectively to-separate piices orbrackets ii and 32, which in turn are welded to the supporting rods 20.

With this arrangement, it can be seen that the heating current suppliedto the cathode supporting rods 20, will flow through the lengths of thecathodes Cl and C2 in series. For example, the

' heating current may flow upward in the cathode Cl and downward in theother cathode C2, the cathode header 25 constituting an electricalconnection between the upper ends of these cathodes. The insulatingtubes 22 serve to electrically isolate the cathode header 25 and theupper ends of the cathodes Cl and C2, from the supporting rods 20, towhich the lowerends of these cathodes are attached. It can be seen thatthe only voltage applied across these insulators 22 is that of theheating circuit for the cathodes. 'Also, these insulators 22, as well asthe resilient element 21, are located in the upper end of th tubesomewhat remote from the high temperature area of the tube. The anode Afor the tube structure of this invention preferably comprises a sheet oftantalum, molybdenum or similar metal of a width correspondingapproximately with the lengths or the gridbars and cathodes, which isbent or rolled and 8 welded together, as indicated at 35 in Pig. 5, intoa tubular form having an outside dimension slightly less than the innerwalls of the tube envelope E. This anode A is held in place andprincipally supported by engagement with the walls of the envelope E,but is maintained out of direct contact with the glass walls of theenvelope for the greater part of its area, and except for some widelyseparated points of contact of limited area suitable for affording thedesired friction with the envelope walls to hold the anode in place. Inthe arrangement shown, a filament or wire 35 of a suitable heatresistant material is wrapped around the anode A in a number of turns,with these turns welded to the anode at a number of points. One type ofspacing element suitable for this purpose comprises a wire of tungstenor the like coated with aluminum oxide or like heat resistent material.Another expedient is to wind around the anode A a round filament orstrip formed of closely wound turns of fine wire. Other expedients, inthe way of spaced protuberances formed in the anode itself, or separatorpieces or strips attached to the outer surface of the anode A may beemployed to accomplish a particular result. The purpose of theseexpedients just described is to hold the sheet metal anode A in place byits frictional engagement with the inner walls of the glass envelope E,but maintain such a space between-the greater part of the surface ofthis anode and these glass walls that heat will be dissipated from theanode by radiation through. these walls, rather than by conduction, sothat the anode may be operated at a high temperature without overheatingthe glass 'walls of the envelope E.

The necessary external electrical connection to the anode A may be madein any convenient manner, such as by a rod 31 welded thereto and in turnwelded to a lead-in wire 38 sealed in the envelope in the usual way atits upper end opposite the press li supporting the grid bars andcathodes. Such location of the lead-in connection for the anode at theopposite end of the envelope from the lead-in connections for thecathode enables high anode voltages to be empioyed.

Various expedients may be employed to assemble the tube structure shown.For the particular type of envelope and seals illustrated, it iscontemplated that a lead-in connection. 38 of sumcient length will bethreaded through the opening for its seal lengthwise of the envelope Eprior to forming of the press I! at the lower end of this envelope.After the weld between the anode con-.

nection I1 and this lead-in wire 38 is made, the anode A may he slippedinto the envelope E, and the seal ior the lead-in wire 38 formed. It iscontemplated that the anode A will be suiliciently like the envelope Ein dimensions that the spacing elements, such as the wire 35 wrappedaround this envelope, will contact with the walls of the envelope at asuflicient number of points to hold it in place. In this connection, itis assumed that the wire 35 will be loosely wrapped around the envelopeand welded thereto at various points to provide turns yieldable forportions of their length, so as to afford the desired supporting contactbetween such portions of the wire 35 and the walls of the envelope. Ifthis spacing element is a strand or strip of finely coiled wire, theresiliency of the coils assist in providing the desired frictionalengagement.

The grid bars and cathodes are mounted and s assembled on the supportingrods l2 and a, the

- 9 welding of the brackets SI and 32 for the cathode being made afterthe desired tension for the spring 21 has been established. Thisassembly of grid bars and cathodes on the supporting rods l2 and 20 maythen be inserted within the anode A inside of the envelope E; and afteralignment of the parts, and while the rods l2 and 20 are held in asuitable clamping device, the glass of the envelope E may be softenedand the press I! formed by a die block or the like in accordance withrecognized practice.

After the assembly and mounting of the tube has been completed, it issubjectedto the appropriate procedure for thorough out-gassing,activation of the cathodes and evacuation, using for this purpose anexhaust tube indicated at 4, to be later sealed oil in the usual way.Such exhaust and cathode activation procedure to establish a high vacuummay be in accordance with recognized and established practice, withoutany special or unusual steps. It is generally expedient to provide apreliminary de-gassing by heating in a vacuum system the wire used forforming the spring 21; and if desired, such preliminary de-gassing canbe applied'to advantage to some of the other parts, thereby avoiding theneed for heating such parts to as high a temperature for as long a timeduring the final operation of outgassing and evacuating the tube. Inthis connection, it will be noted that the anode is a continuous tube,and hence may be readily heated to the appropriate out-gassingtemperature by induction heating or bombing, while other parts,

such as the insulators 22 and spring 21; are kept at lower temperatures.

From the foregoin explanation in connection .assembly afiords thedesired stability and the spaced relationship of the essential partsunder operating conditions, together with an electrical isolation orinsulation between the electrodes permitting the use of high voltages.

It should be understood that the specific construction/ and arrangementof parts shown and described are merely typical or representative of theinvention and are susceptible to various changes without altering theirpurposes and functions. For example, instead of sealing the grid bar andcathode supporting rods I 2 and 20 into the press l3 of the envelope Eafter these grid bars and cathodes have been mounted on these supportingrods, these rods may be sealed in a separate stem mount, the grid barsand cathodes mounted and ali ned on the rods, and then the stem mountfused to thewalls of the envelope E,

in accordance with well known practice. This is merely one example ofhow the structure illustrated may be changed or adapted in accordancewith the skill and practices of the art as may be expedient; and itshould be understood that various modifications, adaptations andadditions may -10 tiall equally spaced parallel relation and connectedat their ends by flexible members with said grid supporting post, a.plurality of elongated thermionic emissive cathodes one between eachadjacent pair of grid bars and extending substantially paralleltherewith, means supporting said cathodes at their ends and maintainingan endwise tension thereon when heated, and an anode around said gridbars and cathodes, said supporting means for said cathodes includinginsulators located outside of said anode electrically isolating theopposite ends of said cathodes to permit heating current to be conductedlengthwise of said cathodes in opposite directions.

2. An electron discharge tube of the character described comprising, abox-like anode, a multicellular structure of fiat elongated grid barsand filamentary cathodes arranged alternately in substantially parallelrelation inside and between opposing surfaces of said anode, a pluralityof parallel supporting rods for said cathodes, a cathode headerresiliently supportedby said rods near one end thereof and insulatedtherefrom, said cathodes being secured at one end to said header atspaced intervals, means connected with said supporting rods foranchoring thereto the other ends of said cathodes, and other supportingmeans cooperating with the ends of said grid bars to position them in apredetermined relation to said cathodes and anode.

3. An electron discharge tube of the character described for use in across-magnetizing magsaid means including a movable cathode headersecured to one end of all of said cathodes and resilient means acting onsaid header to provide heated.

be made with respect to the specific embodiment 4. An electron dischargetube of the character described comprising, a plurality of substantiallyequally spaced filamentary cathodes disposed in a common plane betweenopposing anode surfaces, a pair of supports for said cathodes, meansanchoring said cathodes separately at one end to said supports, acathode header secured to the other ends of said cathodes, insulators onsaid supports supporting the ends of said header to permit movementthereof lengthwise of the cathodes, and means including a resilientelement between said insulators and said header for exerting an endwisepull on the cathodes when heated.

.5. An electron discharge triode of the character described for use ineras-magnetizing fields, comprising a plurality of fiat elongated gridbars arranged at substantially equally spaced intervals in parallelrelation, a plurality of supporting rods outside of said grid bars andextending beyond the ends thereof, a cathode header extending betweensaid supporting rods adjacent one end of said grid bars, means includinginsulating elements slidably supporting said cathode header on saidsupporting rods, a plurality of filamentary thermionic emissive cathodesdisposed one between each adjacent pair of grid bars and secured at oneend to said header, means anchoring the other auasre' l1 ends of saidcathodes tosaidsnpportingrodaand means including a resilient elementinterposed between said headerandsaidsupportingrodsforexerting'tensiononsaidheadertoprovidean endwise pullonsaidcathodeswhenheated.

dAhardvacuumiriodeformeinacrossmagnetisingmagncticiieldcomprisingthreeelongatediiat grid bars arranged at mbstantially equally spaced intervals inparallel relation, two

vfilamentarycathodesextendinglengthwisehe- 12 athodesandeiongatedflatgridbarsdisposedin parallelrelationwithinsaidanode,andmeans attheotherendofsaidenvelopeprovidingsup-7.Atubestructureofthecharacterdescrlbed for use in cross-magnetizingmagnetic fields comprising, a box-like anode having opposing parallelsurfaces disposed in planes parallel with the lines of force of themagnetic field, a plurality ofnarrowelongatedflatgridbarsarrangedinparaliel relation between saidanode surfaces at substantially equally spaced intervals, a plurality'offilamentary cathodes of flattened nickel tubing coated with a thermionicemissive coating and disposed edgewise to said anode surfaces, meanssupporting said cathodes one between each adjacent pair of said grldbars to extend lengthwise thereof throughout their length, said means includinga metallic header to which said cathodesareconnectedatoneendandaresilientelement acting on said header formaintaining tension on said cathodes.

8. Atube structureotthechamterdescribed, comprising with a plurality ofspaced parallel filamentary thermionic emissive cathodes, a plurality ofelongated grid bars disposed in parallel relation at substantiallyequally spaced intervals on oppodte sides of said cathodes, asinglesupporting rod for said grid bars extending longitudinally thereofand attached to an intermediate grid bar, andresilient supportsconnecting together said gridbarsatthelrendssaidsupporishavmg openingsfor the cathodes,

9. An electron discharge tube of the character decribed comprising, aplurality of filamentary thermionic emissive cathodes disposed in asubstantially equally spaced parallel relation in a common plane betweenopposing anode surfaces, and a plurality of elongated flat grid barsdisposed in parallel relation .at substantially equaldistancesbetweensaidcathodeasaidgrldbars being formed with flanges forlateral stillness, flexible elements connecting said grid bars togetherat their ends with openings for said cathports and lead-in connectionsfor said cathodes 11. Anelecirondischargetubeofthetypedescribedcomm-icing, a plurality of filamentary thermionic emissive cathodes andlist elong ted rfii bars arranged alternately in parallel relaticn, aglass envelope, means providing separate lead-in connections andsupports for said grid bars and cathodes from one end of said envelope,

a sheet metal anode surrounding said grid barsandcathodesandsmmortedbythewallsofthe envelope but separated therefromby heat resistant spacing elements. and a lead-inconnecflonforsaidanodeattheotherendofsaid envelope.

12. An electron discharge tube of the character described comprising, aplurality of cathodes and grid'bars in a multicellular assembly, a glassenvelope of general elliptical cross section, a. sheet .1

metal anode of non-magnetic material surrounding said assembly, ofcathodes and grid bars within said envelope, said anode being closelyspaced to the inside sin-fac of said envelope, and heat resistantelements attached to the outer surface of said anode and contacting withthe walls of said glass envelope at a plurality of points to maintainsaid anode in position within the envelope, and a lead-in connection forsaid anode extending through a gas-tight seal in said envelope.

13. An electron discharge tube of the characacter dwcribed, comprising aflattened glassenvelope of general elliptical cross section, an anodemade of a thin sheet of non-magnetic metal and shaped to conform withthe inner surface of said envelope, and a plurality of turns of a heatinsulated wire around said anode contacting with v the surface of saidenvelope to provide a support for said anode while maintaining saidanode out of contact with the walls of said envelope for a large part ofits area to permit direct radiation of heat from the anode through thewalls of the envelope.

14. An electron discharge tube of the character described for use in amagnetic field acting substantially at right angles to the axis of thecathode of the tube comprising, an evacuated envelope, a plurality offilamentary thermionic emissive cathodes and flat elongated grid barsarranged alternately in parallel relation with the said envelope, a pairof parallel supporting posts sealed in one end of said envelope andconstituting supports and lead-in connections for said cathodes, a pairof steatite insulators on said posts near one end,a cathode header towhich odes,andmeanssupportingsaidgridbars,said

eralellipticalcrosssectimasheetmctal anode within said envelopesupported by thejwalls thereof but separated from said wallsfby heatresistant elements, a lead-in connection for said anode at one end ofsaid envelope. at multicellunctic field comprising, a glass envelope ofgensaid cathodes are connected at one end, said header being slidablymounted on said insulators for movement lmgthwise of the cathodes, saidcathodes being connected at their other ends to sail posts, andresilient means cooperating with saidpostsandsaidheadertoexertan endwisepull on said cathodes.

15. An electron discharge tube of the character described comprising, amulticellular assembly of a plurality of filamentary cathodes andelongatedgrid bars arranged alternately in parallel relation, a singlesu rting rod for said grid bars extending longitudinally thereof andattached to an intermediate grid bar, meansconnectingsaidgridbarstogetherattheirendsto permit endwise expulsionthereof, and means in- -larstructureofiiiammtarythermionicemissive 7iclodhigapah-ofsupportingpostsoutsideofsaid 13 grid bars and supportingsaid cathodes at their ends.

16. An electron discharge tube comprising three elongated grid elementsdisposed at substantially equal distances in parallel relation, a pairof filamentary cathodes extending lengthwise of said grid elements atsubstantially equal distances therefrom, a supporting rod for said gridelements, and a pair of supporting rods and insulators thereon forsupporting said cathodes and connecting them in series for heatingcurrent supplied to said pair of supporting rods.

17. An electron discharge tube comprising a glass envelope of flattenedcross-section with two of its walls in a relatively close spacedparallel relation, an assembly of a plurality of filamentary cathodesand elongated grid elements in parallel relation, an anode around saidassembly having its outer surface closely spaced to the inner walls ofsaid envelopes, and spacing elements attached to the outer surface ofsaid anodes and having frictional contact with the envelope walls over alimited portion of the anode surface for supporting said anode by saidenvelope while permitting heat from the anode to be dissipated largelyby radiation through the envelope walls.

18. A controllable electron discharge tube of the hard vacuum type foruse in a cross magnetizing magnetic field comprising, an envelope with astem mount at one end, a multicellular assembly of a pair of filamentarycathodes and a plurality of elongated grid bars arranged alternately insubstantially equally spaced parallel relation, a single supporting postsupporting said grid bars and sealed in said stem mount of the envelope,a pair of cathode supporting rods extending lengthwise of said assemblyand sealed in said stem mount in the envelope, said cathodes beingconnected at one end separately to said rods, an electrical connectionbetween said cathodes at their other ends, and means including heatresistant insulating material connected with said rods and acting toslideably support said cathodes at their electrically connected ends.

19. A tube structure for use in a cross magnetizing magnetic fieldcomprising, a box-like anode, an assembly of elongated grid bars andfilamentary cathodes arranged alternately in substantially equallyspaced parallel relation inside said anode with said grid bars edgewiseto opposing surfaces of said anode, an envelope of flattenedcross-section with two of its sidewalls closely spaced to said opposingsurfaces of said anode, a single grid supporting post sealed in one endof said envelope and attached to one of said grid bars, flexible meansconnecting said grid bars at their ends to permit independent endwiseexpansion, a pair of cathode supporting rods sealed in said end of theenvelope, and means supporting said cathodes on said rods and permittingheating current to be conducted from said rods lengthwise through thcathodes.

DONALD V. EDWARDS. WARREN G. BROWN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,748,175 Holden Feb. 25, 19301,754,120 Robinson Apr. 8, 1930 2,221,743 Wagner Nov. 12, 1940 2,248,712Litton July 8, 1941 2,332,977 Skellett Oct. 26, 1943

